This adds a full functional test for starting up an SNTApplication
(with as few mocks as possible) and executing it with a directly
recorded & collected EndpointSecurity event.
This also fixes a potential race condition and segfault on Santa startup: due
to es_subscribe being called first, it's possible for an es event to arrive
before listenForDecisionRequests or listenForLogRequests are called,
causing the SNTEndpointSecurityManager callbacks to call a nil pointer.
